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Quantification and ecological study of ‘Candidatus Liberibacter asiaticus’ in citrus hosts,rootstocks and the Asian citrus psyllid 
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下载免费PDF全文 The use of proper management strategies for citrus huanglongbing (HLB), caused by ‘Candidatus Liberibacter asiaticus’ (Las) and transmitted by Asian citrus psyllid (ACP) (Diaphorina citri), is a priority issue. HLB control is based on healthy seedlings, tolerant rootstock cultivars and reduction of ACP populations. Here, dynamic populations of Las in different citrus hosts and each instar of ACP were studied, together with the seasonal growth and distribution of Las in different tissues, using conventional and TaqMan real‐time PCR. Different levels of susceptibility/tolerance to HLB were seen, resulting in different degrees of symptom severity and growth effects on hosts or rootstocks. Troyer citrange, Swingle citrumelo and wood apple were highly tolerant among 11 rootstock cultivars. Regarding distribution and seasonal analysis of Las, mature and old leaves contained high concentrations in cool temperatures in autumn and spring. Las was detected earlier through psyllid transmission than through graft inoculation, and the amounts of Las (AOL) varied in different hosts. Thus, different AOL (104–107 copy numbers μL?1) and Las‐carrying percentages (LCP; 40–53.3%) were observed in each citrus cultivar and on psyllids, respectively. Furthermore, both AOL and LCP were lower in nymphs than in adult psyllids, whereas the LCP of psyllids were not affected by increasing the acquisition‐access time. The present study has significant implications for disease ecology. The combination of early detection, use of suitable rootstocks and constraint of psyllid populations could achieve better management of HLB disease. 相似文献
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A. P. Martínez‐González H. D. Ardila S. T. Martínez‐Peralta L. M. Melgarejo‐Muñoz M. A. Castillejo‐Sánchez J. V. Jorrín‐Novo 《Plant pathology》2018,67(8):1647-1668
Plant pathogens have developed different strategies during their evolution to infect and colonize their hosts. In the same way, plants have evolved different mechanisms acting against potential pathogens trying to infect and colonize their tissues. Regulation of a wide variety of proteins is required in order to perceive the pathogen and to activate the plant defence mechanisms. The apoplast is the first compartment where these recognition phenomena occur in most plant–pathogen interactions, allowing the exchange of different molecules and facilitating inter‐ and intracellular communication in plant cells. Proteomic analysis of the apoplast in recent years has found the initial biochemical responses involved in pathogen recognition and early defence responses. However, this proteomic approach requires some specific experimental conditions to obtain an extract free of cytoplasmic proteins and nonprotein contaminants that affect the subsequent stages of separation and quantification. Obtaining the highest proportion of proteins from the apoplastic space in infected tissues requires different steps such as extraction of apoplastic washing fluids and preparation of total secreted proteins (protein precipitation, solubilization, separation and digestion). Protein identification using mass spectrometry techniques and bioinformatics tools identifying peptides for the extracellular exportation is required to confirm the apoplastic location. This review compiles the most commonly used techniques for proteomic studies, focusing on the early biochemical changes occurring in the apoplast of plants infected by a wide range of pathogens. The scope of this approach to discover the molecular mechanisms involved in the plant–pathogen interaction is discussed. 相似文献
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Role of strawberry volatile organic compounds in the development of Botrytis cinerea infection 下载免费PDF全文
下载免费PDF全文 F. Neri L. Cappellin A. Spadoni I. Cameldi A. Algarra Alarcon E. Aprea A. Romano F. Gasperi F. Biasioli 《Plant pathology》2015,64(3):709-717
Botrytis cinerea, the main pathogen of strawberry, has the ability to remain quiescent in unripe tissue and develop disease symptoms in ripe fruit. As strawberry ripening is characterized by an increase of aroma compounds, the role of volatile emission in the development of infection was investigated. Thirty‐five strawberry volatile organic compounds (VOCs) were tested on B. cinerea in vitro and volatile emission was analysed in strawberry harvested at four ripening stages by headspace solid‐phase microextraction/gas chromatography–mass spectrometry and proton transfer reaction–time of flight–mass spectrometry. The coupling of such data sets made it possible to conclude that key strawberry aroma compounds stimulate B. cinerea conidial germination and some typical wound‐volatiles stimulate pathogen conidial germination or mycelial growth. This study is the first report of fungal stimulation by some VOCs naturally occurring in strawberry: the esters ethyl butanoate, cis‐3‐hexenyl acetate, trans‐2‐hexenyl acetate, methyl butanoate and hexyl butanoate, the furanones furaneol and mesifurane, and the alcohol trans‐2‐hexenol. The results of this work provide advances in understanding the functional role of fruit VOCs and suggest, for the first time, that fruit VOCs may influence the development of B. cinerea from the latent phase and that they could favour the invasive growth of B. cinerea after wounding. In particular, ethyl butanoate and furaneol could signal strawberry ripening, and the green leaf volatiles trans‐2‐hexenol, trans‐2‐hexenyl acetate and cis‐3‐hexenyl acetate could signal the presence of damaged tissues that are easier sites for penetration by B. cinerea. 相似文献
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Non‐target‐site mechanism of glyphosate resistance in Italian ryegrass (Lolium multiflorum) 下载免费PDF全文
下载免费PDF全文 Kohei Kurata Yuki Niinomi Yoshiko Shimono Masahiro Miyashita Tohru Tominaga 《Weed Biology and Management》2018,18(3):127-135
In Shizuoka Prefecture, Japan, glyphosate‐resistant Lolium multiflorum is a serious problem on the levees of rice paddies and in wheat fields. The mechanism of resistance of this biotype was analyzed. Based on LD50, the resistant population was 2.8–5.0 times more resistant to glyphosate than the susceptible population. The 5‐enolpyruvyl‐shikimate‐3‐phosphate synthase (EPSPS) gene sequence of the resistant biotype did not show a non‐synonymous substitution at Pro106, and amplification of the gene was not observed in the resistant biotype. The metabolism and translocation of glyphosate were examined 4 days after application through the direct detection of glyphosate and its metabolite aminomethylphosphonic acid (AMPA) using liquid chromatograph‐tandem mass spectrometer (LC‐MS/MS). AMPA was not detected in either biotype in glyphosate‐treated leaves or the other plant parts. The respective absorption rates of the susceptible and resistant biotypes were 37.90 ± 3.63% and 41.09 ± 3.36%, respectively, which were not significantly different. The resistant biotype retained more glyphosate in a glyphosate‐treated leaf (91.36 ± 1.56% of absorbed glyphosate) and less in the untreated parts of shoots (5.90 ± 1.17%) and roots (2.76 ± 0.44%) compared with the susceptible biotype, 79.58 ± 3.73%, 15.77 ± 3.06% and 4.65 ± 0.89%, respectively. The results indicate that the resistance mechanism is neither the acquisition of a metabolic system nor limiting the absorption of glyphosate but limited translocation of the herbicide in the resistant biotype of L. multiflorum in Shizuoka Prefecture. 相似文献
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The adsorption processes of carbofuran from an aqueous solution have been determined at the solid–liquid interface, onto silica and at liquid–vapour interfaces. At the solid–liquid interface, the adsorption isotherms and their evolution with temperature reveal that adsorption is generally weak but increases with temperature. Adsorption also significantly increases with concentration when the solubility limit is approached. The study at the liquid–vapour interface reveals that adsorption at this interface is 70 times larger than at the solid–liquid interface. Again, adsorption values at the liquid–vapour interface increase with temperature (below 30°C) and near the solubility limit. Consequences of the observations on the behaviour of carbofuran in the environment are discussed. © 1998 SCI 相似文献
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Frequency and occurrence of the carrot pathogen ‘Candidatus Liberibacter solanacearum’ haplotype C in Finland 下载免费PDF全文
下载免费PDF全文 M. Haapalainen P. Kivimäki S. Latvala M. Rastas A. Hannukkala L. Jauhiainen A. Lemmetty M. Pirhonen A. Virtanen A. I. Nissinen 《Plant pathology》2017,66(4):559-570
Occurrence of ‘Candidatus Liberibacter solanacearum’ (CLso) was studied in field‐grown carrots (Daucus carota) in different regions of Finland. In addition, the frequency of CLso in carrots and in field populations of its vector, the carrot psyllid (Trioza apicalis), was studied in southwestern Finland. CLso was detected in six of the seven regions where the main carrot cultivation areas are located. The highest disease incidence was found in southwestern Finland, in the area where this carrot pathogen was originally found. In the Tavastia Proper and Southwest Finland regions, CLso was detected in 26 out of 30 randomly chosen fields inspected in 2013 and 2014, and in a third of those fields more than 10% of plants showed symptoms. Of those carrots showing both psyllid feeding‐associated leaf curling and CLso infection‐associated leaf discolouration symptoms, 77% were CLso positive in the PCR test. Some symptomless carrots from the affected fields also tested positive. Of the carrot psyllid individuals collected from the same area, 60% were CLso positive. Elsewhere, disease incidence was variable in South Ostrobothnia in western Finland and low but established in South Savonia in eastern Finland. CLso was not detected in the North Ostrobothnia region. Sequencing of the amplified DNA fragments confirmed that the bacteria in the carrot samples from different areas within Finland all represented CLso haplotype C. The frequent occurrence and wide distribution of this pathogen, transmitted by a psyllid that does not migrate over long distances, suggest that it is persistent in Finland. 相似文献
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Kazuhiko Matsuda Steven D Buckingham John C Freeman Michael D Squire Howard A Baylis David B Satelle 《Pest management science》1999,55(2):211-213
Examination of agonist interactions of imidacloprid on recombinant chicken α4β2 and Drosophila SAD/Chicken β2 hybrid receptors, expressed in Xenopus oocytes by nuclear injection of the cDNAs, indicates that imidacloprid is a partial agonist. Replacement of the α4 subunit for the Drosophila SAD subunit lowered the imidacloprid EC50 37-fold, whereas EC50s for other agonists increased 4-50 fold, suggesting that the α subunit contributes to the high affinity of insect nicotonic receptors for imidacloprid. ©1999 Society of Chemical Industry 相似文献
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The immunodominant membrane protein Imp of several phytoplasmas within the ‘Candidatus Phytoplasma aurantifolia’ (16Sr‐II) group was investigated. Eighteen isolates from Iran (11), East Asia (5), Africa (1) and Australia (1) clustered into three phylogenetic subgroups (A, B and C) based on the 16S rDNA and imp genes, regardless of geographic origin. The imp gene sequences were variable, with more non‐synonymous than synonymous mutations (68 vs 20, respectively), even though many of the non‐synonymous ones (75%) produced conservative amino acid replacements. Eight codon sites on the extracellular region of the protein were under positive selection, with most of them (75%) coding for non‐conservative amino acid substitutions. Full‐length (21 kDa) and truncated (16 kDa) Imp proteins of two economically important Iranian phytoplasmas [lime witches’ broom (LWB) and alfalfa witches’ broom (AlWB‐F)] were expressed as His‐tagged recombinant proteins in Escherichia coli. An antiserum raised against full‐length recombinant LWB Imp reacted in western blots with membrane proteins extracted from LWB‐infected periwinkle and lime, indicating that Imp (19 kDa) is expressed in infected plants and is a membrane‐associated protein. The same polyclonal antibody also detected native Imp in proteins from periwinkles infected by phytoplasmas closely related to LWB (subgroup C) only, confirming phylogenetic clustering based on 16S rDNA and imp genes. Imp proteins of LWB and AlWB‐F isolates were also recognized by an antiserum raised against an enriched preparation of AlWB‐F phytoplasma cells, demonstrating the antigenic properties of this protein. 相似文献
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A yellows disease system with differing principal host plants for the obligatory pathogen and its vector 下载免费PDF全文
下载免费PDF全文 R. Sharon A. R. Harari T. Zahavi R. Raz M. Dafny‐Yelin M. Tomer C. Sofer‐Arad P. G. Weintraub V. Naor 《Plant pathology》2015,64(4):785-791
A stolbur‐type phytoplasma is the putative pathogen of grapevine yellows disease that causes economic damage to vineyards in most growing areas around the world. The pathogen is known to be transmitted to vines by two planthoppers, Hyalesthes obsoletus and Reptalus panzer; the latter is found in Europe but has not yet been observed in Israel. The establishment of a vector–pathogen–plant relationship requires that the pathogen and the vector meet on a shared host plant. This does not happen in the ecosystem examined here, where two different principal host plants for the obligate pathogen and its vector exist: the pathogen is established on vines, while its vector, H. obsoletus, develops on Vitex agnus‐castus. The present study verified that: (i) the vector cannot complete its life cycle on vines; (ii) V. agnus‐castus does not grow in the immediate vicinity of vines, and does not harbour the pathogen; and (iii) the pathogen is not vertically transmitted from mother to offspring. Moreover, in a thorough search of plants in vine growing areas, no other plants were found that host both the vector and the pathogen. However, it was found that the planthopper can acquire the phytoplasma from infected vines. Nonetheless, this does not prove the ability of the planthopper to further transmit the pathogen to vines and does not explain the presence of the vector on the non‐preferred vines. Thus, the enigma of the pathogen–vector–host triangle in this system remains unresolved. 相似文献
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A Simple PCR-based Method for the Detection of the Chickpea-wilt Pathogen Fusarium oxysporum f.sp. ciceris in Artificial and Natural Soils 总被引：1，自引：0，他引：1
M.D. García-Pedrajas B.W. Bainbridge J.B. Heale E. Pérez-Artés R.M. Jiménez-Díaz 《European journal of plant pathology / European Foundation for Plant Pathology》1999,105(3):251-259
A fast and simple polymerase chain reaction method has been developed for the detection of Fusarium oxysporum f.sp. ciceris, the causal agent of Fusarium wilt of chickpea, in natural and artificial soils. The method involves the disruption of fungal biomass by grinding dry soil, using its abrasive properties, in the presence of skimmed milk powder. The latter prevents loss of DNA by adsorption to soil particles or by degradation and reduces the co-extraction of PCR inhibitors with the DNA. After phenol/chloroform extraction, the DNA is suitable for direct PCR amplification without a precipitation step. For the efficient detection of small amounts of DNA extracted from soil, a two step amplification with nested primers was used. The dilution step reduced the effect of Taq-polymerase inhibitors. The specificity of the amplification, and consequently the yield of specific product, was increased by the use of a modified touch down process during the annealing step. The method has been applied to the specific detection of wilt-inducing isolates of the pathogen in a variety of natural and artificial soils. The amplification was improved by the use of increased concentrations of skimmed milk powder in soils with high organic or clay contents. 相似文献
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作为美国国家科学基金项目"中国生态恢复综合影响评价"的部分研究结果,对项目选定的四个评价区之一的黄河中上游地区的研究区域进行土地利用和覆盖变化研究,并以此评价退耕还林效果。利用覆盖研究区域的卫星遥感图像进行解译,以便获取研究区域土地利用和土地覆盖变化(LUCC)的历史数据,特别是大于25度坡度的LUCC以及退耕前后的LUCC数据,通过这些解译数据评价研究区域的退耕还林效果。解译后的数据显示退耕还林效果良好。选定24景跨20年(1978年至2007年)的Landsat遥感卫星图像数据,通过解译追踪研究区域LUCC历史演变,来判断退耕还林的执行效果。 相似文献
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